Method of sealing a member in an opening in a body



Feb. 17, 1970 I P. D. c. MORRIS METHOD OF SEALING A MEMBER IN AN OPENINGIN A BODY Filed May 5, 1967 United States Patent US. Cl. 29157 4 ClaimsABSTRACT OF THE DISCLOSURE A seal is made between, for example, acircular bolt head and a close-fitting housing by a plastic sleeve whichis cut on its inside face as the bolt head is forced home to be turnedinto a perfectly-mating cup washer.

This invention relates to arrangements for sealing an annular bodyportion in a cylindrical body portion. Specifically, the inventionrelates to arrangements for sealing two such portions together, where itis required to occupy a clearance between the two members so that thisclearance cannot be penetrated by ambient liquid. The invention alsorelates to means being provided whereby an annular body portion may besealed around a close-fitting cylindrical body portion whilst permittingthe two portions to be removed from one another without difiiculty at alater time.

Circumstances often arise in which two body portions, for example, twoapparatus or machine parts, have to be fitted one into the other, wherea clearance therebetween has to be sealed. Sometimes, this seal isrequired to prevent the transmission of fluid, and at other times it isrequired merely to prevent the establishment of a pocket of liquid incircumstances where bacterial decomposition may otherwise be initiated.One particular example is the case where the cylindrical head of athreaded member is received into a corresponding recess in anothermember when the two are screwed together. To establish a seal it is ofcourse possible to have the head engage against a flat annular washerhoused inside a counterbore in the other member, but this still leaves acylindrical clearance. w

The invention consists in a method of sealing a clearance between acylindrical body member and an encircling annular body member whichcomprises fitting a sleeve of a ductile plastics material in the annularbody member, and forcing the cylindrical body member into position withan interference fit between it and the sleeve so that a radially innerlayer of the sleeve is cut away by the advancing cylindrical member andforced downwardly against a seat associated with the annular body memberwhilst at the same time the sleeve is pressed radially outwardly againstthe inner face of the annular body member in which it is fitted, thusconverting the sleeve into an accurately fitting cup washer.

The invention has particular reference to the case where the cylindricalbody member is the head of a screw threaded bolt and the annular bodymember and seating are defined by a counterbore in which the head isreceived. In this case, the bolt is initially sealed into positioncutting its way through the sleeve and thus accurately dimensioning theremainder of the sleeve to occupy the space between the annular andcylindrical body members.

The expression cylindrical body member will be understood to mean acircular body or portion of a larger 3,495,314 Patented Feb. 17, 1970body whether solid or apertured. The expression annular body member willbe understood to mean a body or part of a body having a cylindricalinner face in which the cylindrical body member will fit, and theexpression ductile plastics material" will be understood to mean aplastics material the surface layers of which can be cut away by anadvancing square-edged body ploughing through the surface layers of thesame to leave a smooth coherent surface behind and without the cut-awayportion breaking up into chips or powder. Polytetrafluoroethylene hasbeen found particularly suitable for this purpose, its low coefiicientof friction with respect to metal permitting subsequent withdrawal ofthe annular body member when required.

The present method of providing a seal finds particular application infood machinery where pockets in which bacterial decomposition can becomeestablished are to be avoided. One specific application of the inventionlies in the mounting of tubular edge filter assemblies in divi sionplates for use in for example the filtering of beer. It has beencustomary to bore and thread a division plate by screwing them intothreaded engagement within the corresponding bores. To avoid anundesired pocket at the top of the division plate, it has been customaryto provide that the head of each edge filter disc assembly overlies thetop of the division plate, the latter thus not being counterbored toreceive the head. Even so, problems have arisen from the clearancebetween the disc assembly and the lower part of the bore, on the side ofthe division plate remote from the aforementioned head. In thisparticular application of the invention, it is preferred that the borein the division plate should not itself be theraded but instead shouldbe occupied by an annular insert which can be located by expanding itagainst the interior of the bore through the division plate. This insertis threaded and itself provides the equivalent of a counterbore on theupper side of the division plate by restricting the lower part of saidbore. According to the invention, a sleeve of ductile plastics materialsuch as polytetrafluoroethylene is inserted as a close fit in thiscounterbore and the edge filter disc assembly is screwed into position.According to a further feature of the invention, the edge filter discassembly is furnished with a sealing ring, suitably an O-ring which maybe of a conventional high polyacrylonitrile synthetic rubber, located toseal against the inner face of the insert just below a threaded portionthereof substantially level with where the assembly emerges below theinsert. In this way, the formation of any pocket of liquid (such asbeer) to be filtered is prevented both above and below the division pate.

The expression interference fit used herein should be understood asmeaning that the external diameter of the annular body member exceedsthe internal diameter of the sleeve of plastics material so that thelatter is cut and/or plastically deformed to assume the form of anaccurately fitting cup washer as the annular body member is forced home.In one example, the dimensions of the various parts are such that thewall and base of the resulting cup washer are each of the order of 14mms. thick.

One embodiment of the invention is illustrated in the accompanyingdrawing, which is a longitudinal sectional view of a filter elementmounted in a division plate of a sterile beer filter, only a fragment ofthe division plate being shown.

The filter element comprises a stack of edge filter discs 1 clampedbetween the head 2 of a bolt 3 and a cylindrical nut 4 into which thebolt screws. The bolt 3 is formed with longitudinal collecting channels5 along which liquid which has penetrated radially inwardly between thediscs 1 can drain to an outlet 6. The filter element is supported in adivision plate 7, which may typically be a substantial steel plateformed with a considerable number of bores each accommodating the upperend of one filter element. In a typical example, the division plate maybe perhaps 4 or 5 feet in diameter, about 2 inches thick and may carryover 100 filter elements.

In the drawing, only one such bore 8 is illustrated. This has a flangedsleeve 9 inserted from the underside, this sleeve being threaded toengage a corresponding thread on the exterior of the nut 4. Below thethreaded part of the sleeve 9 the sleeve seals against the shank of thenut 4 by means of an (I -ring 10 carried in a groove in the aforesaidshank (or alternatively in the flanged sleeve 9). Before the nut 4 isfitted the sleeve 9 is anchored securely in position by being expandedradially outwardly through the application of a suitable expanding toolto the inner bore of the sleeve at the lower end, below the threadedpart.

Also, prior to the insertion of the nut 4, a cylindrical washer 11 ofpolytetrafiuoroethylene is inserted as a close fit in the bore 8 tolodge against the upper end of the sleeve 9. The nut 4 has an enlargedhead 12 which is an interference fit with the washer 11 so that, as thenut 4 is screwed home, the head 12 bites into the radially inner part ofthe washer 11, pares the surface layers away and collects these togetherunder the head 12 in the form of a flat ring 13 integrally with theremainder of the sleeve 11 so that the polytetrafiuoroethylene nowassumes the form of a cup washer 11, 13. This cup washer is an extremelyaccurate it with respect to the head 12 of the nut 4 and the surroundingbore 8 of the division plate 7 .so that the nut 4 can be withdrawn toremove the filter element and then replaced. If however a different nut4 is used, that is to say, if the filter element is not replaced in thesame bore after removal for cleaning or other attention, then a freshwasher 11 should be employed.

Th use of the washer 11 and the O-ring 10 serves to isolate the spacebetween the edge disc assembly and the sleeve 9 from the ingress ofliquid undergoing filtration and thus removes one of the major sourcesof contamination in a sterile filter plant. The very accurate fit of thehead of the edge filter disc assembly, that is to say, of the nut 4,into the washer 11 and the very ac- 4 a curate fit of this washeragainst the division plate 7 also serves to prevent the penetration offiltered sterile liquid into an area where it would otherwise bedifficult to prevent the onset of contamination.

I claim:

1. A method of sealing a clearance between a cylindrical body member andan encircling annular body member which comprises fitting a sleeve of aductile plastics material in the annular body member, and forcing thecylindrical body member into position with an interference fit betweenit and the sleeve so that aradially inner layer of the sleeve is cutaway by the advancing cylindrical member and forced downwardly against aseat asso ciated with the annular body member whilst at the same timethe sleeve is pressed radially outwardly against the inner face of theannular body member in which it is fitted, thus converting the sleeveinto an accurately fitting cup washer.

2. A method according to claim 1, wherein the cylindrical body member isin the form of a head on a screw which is screwed into a counterboreline with said sleeve of ductile plastics material.

3. A method according to claim 1, wherein said plastics material ispolytetrafiuoroethylene.

4. A method according to claim 1, applied to the mounting of a tubularfilter body in a division plate, the head of said tubular filter bodyrepresenting said cylindrical body member, the division plate beingsealed to the filter tube at the side where the filter tube protrudes,by an O-ring.

References Cited UNITED STATES PATENTS CHARLIE T. MOON,

US. 01. X.R. 29432, 459; 21o-2a2; 277 212; 2s5 -159 Primary Examiner

